Pressure relief valves are widely used in motor vehicles to relieve air pressure surges or peaks in the passenger compartment which result for example, when the doors are slammed shut. The valves generally comprise a simple rigid frame or housing which mounts in an aperture in a vehicle body panel. A valve element in the form of a flap is connected to the frame to overlie the aperture in the vehicle body panel. The valve element opens relative to the frame to uncover the aperture to relieve air pressure surges.